We are proposing a comprehensive investigation of the structure-activity relationships of conformationally flexible narcotics (opiates). The low energy conformational geometries of a narcotic will be surveyed by correlating the conformational energy, computed using a potential function method, with various intramolecular geometrical parameters. Low energy conformational geometries and pharmacological properties will be correlated for structurally related narcotics and across classes of narcotics. The objective of this is to determine if there are any low energy molecular geometries that are shared by their recently discovered endogenous equivalent, the enkephalins, that can account for their actions at the level of narcotic receptors. This will allow the testing of a number of hypotheses that have been suggested for the conformational requirements of the narcotics. In addition, detailed comparisons will be made between our conformational data and those from experimental sources such as x-ray crystallography and nuclear magnetic resonance. This will insure that our results continue to be physically realistic and will allow further testing of our method of conformational analysis. Efforts will also be made to have experimental verification of our theoretical predictions.